Bascule bridge with central girder leaf support



H. A. LOSER April 3, 1956 BASCULE BRIDGE WITH CENTRAL GIRDER LEAF SUPPORT 4 Sheets-Sheet 1 Filed Feb. 16, 195] I If INVENTOR. Hneev 19. 4056/2 ATTORNEYS April 3, 1956 LOSER 2,740,145

BASCULE BRIDGE WITH CENTRAL GIRDER LEAF SUPPORT Filed Feb. 16, 195] 4 Sheets-Sheet 2 v INVENTOR. v

Hneev H. 4055a 241M *AM H. A. LOSER April 3, 1956 BASCULE BRIDGE WITH CENTRAL GIRDER LEAF SUPPORT Filed Feb. 16, 1951 w 3 m 5 a N a m m4 m p W m H M NM 1 bw v mkm m A Tree's/5w;

H. A. LOSER BASCULE BRIDGE WITH CENTRAL GIRDER LEAF SUPPORT Filed Feb. 16, 1951 4 Sheets-Sheet 4 I H I INVENTOR. 4 0 see Haney 9 BY Mi, Mi 4M United States Patent BASCULE BRIDGE WITH CENTRAL GIRDER LEAF SUPPORT Harry A. Loser, Milwaukee, Wis. Application February 16, 1951, Serial No. 211,417 3 Claims. (Cl. 14- 38) This invention relates to a bascule bridge having a single central girder supporting each leaf.

In my improved bascule bridge, the counter-balance is applied entirely to a central girder of any approved cross section which provides the entire support for the leaf during raising and lowering operations. -Such supplemental girders as may connect the outer ends of the floor beams are used primarily to prevent torsional strains in the central girder and do not sustain any counterweight, and appear as fascia members in the finished structure.

The operating mechanism includes the motor and reduction gear train and driving pinion, all of which may be carried by the single central girder as a part of the counterweight, the operating pinion meshing with a fixed rack of long radius.

The conventional type of bascule bridge has each movable leaf framed and supported by widely spaced longitudinal and parallel girders, each supported on axially aligned trunnions and extending rearward from the trunnions to support a counterweight framed transversely between the girders. This arrangement of the counterweight usually requires a foundation with a pit of sufiicient width and depth to receive the entire rear end of the leaf when in the raised position. The operating mechanism usually consists of two or more gear trains or reduction units rigidly attached to the foundation and geared to pinions which engage a rack of short radius connected to each girder and concentric with its trunnion. The position of the operating machinery, usually placed at a considerable distance ahead of the trunnions, requires a considerable longer span (distance center to center of trunnions) than a fixed bridge spanning the same channel.

The cost of such a bridge is times the cost of a fixed bridge of the same length and width. The three major factors contributing to the increased cost are the large foundations required for the wide pits, the operating machinery, and the increased length of span (distance center to center of trunnions) as compared with the distance between piers.

As compared with such conventional bridges, my improved bascule bridge construction has the following advantages:

1. It saves in the cost of the piers, principally by reducing the size of the pit, which is only required to receive the end of the single girder and localized counterweight, as distinguished from the conventional construction wherein the entire end of the bridge leaf must be accommodated. In a given bridge this saving has been found to be 50%. In others, it may be more or less than this figure but is very substantial.

2. In the bridge in which comparative figures are available, my construction saves more than 50% in the cost of the operating machinery, which can be lighter because of the increased radius of the rack and reduced Weight of the leaf and does not have to be duplicated about two and one-half because its acts on a single rack instead of on two or more widely spaced racks.

'3. In any trunnion bascule bridge, my construction saves between 20% and 30% of the cost of structural steel required. I

4. It saves from 25% to 35% in electrical equipment because the controls are greatly simplified, there being only one set of operating mechanism for each leaf, thus eliminating the means heretofore required for coordinating the two separate driving devices which have heretofore acted on the separate girders.

5. There is a saving of 12 /2% to 50% of other items entering into bridge construction, the overall saving on the entire bridge structure amounting to approximately one-third. I

6. The new construction makes 'it possible to construct a bascule bridge over'skew'ed waterways with a istance center to center of trunnions only slightly greater than would be required fora square bridge spanning the same width of channel.

7. A wider range of aesthetic treatment becomes possible as a result of the new construction, since the primary supporting girder is centrally located and therefore substantially concealed from view.

8. Theweight of the operating machin'ery'is utilized as a counterweight. While there have been bridges suggested in which the operating machinery was carried by the leaf, it was not practical to construct such a bridge or to take advantage of this proposed mounting until the present invention, wherein the use of a single supporting girder for each leaf, and a single operatingmechanisin, make this mounting feasible.

9. The use of a single operating mechanism for each leaf eliminates chatter and racking strains heretofore experienced due to the unequaloperation of the separate motors and separate gear trains heretofore required in thedual girder construction conventionally used.

10. The application of force required to overcome the inertia of the leaf is decreased by the larger rack radius and reduced leaf weight from approximately 3450 pounds in a given bascule bridge of conventional design to only 1120 pounds in a bridge using the design herein disclosed. The bridge in question carries a 42'foot roadway and the conventional design had required a spacing of 115 feet from center to center of the leaf trunnions at opposite sides of the foot navigation channel as compared to feet center to center of trunnions to span 80 feet channel b'yth'e improved bridge. Actual cost figures on a bridge according to the present design showed a saving in cost which amounted to one-third of the entire cost of the conventional bridge. I

In the drawings: 7

Fig. 1 is a plan view of a bascule bridge embodying my invention.

Fig. 2 is a view thereof in side elevation.

Fig. 3 is a view on an enlarged scale showing the bridge pier and the leaf frame in plan, the roadway being omitted to expose the trunnion mounting of the single supporting girder, and the pit into which the rear end of the girder and its counterweight are receivable.

Fig. 4 is a view taken in section on the line 44 of Fig. 3.

Fig. 5 is a detail 55 of Fig. 4.

Fig. 6 is a fragmentary detail view showing a modified embodiment of the Fig. 7 is a view taken in section'on Fig. 6. p

Fig. 8 is a detail view taken in transverse section showing a fur'ther modified embodiment.

As above indicated,- -fny improved bridge structure chinprises for each leaf 9 a single central'supp'ort 10*e5rt'endview taken in section on the line similar to Fig. 4 invention. H

the line 77 'of ing longitudinally of the leaf. As shown in Fig. 5, this support may comprise apair of deep section girders 11, 12, cross connected by plates 13, 14 to function as one box girder. Any suitable cross framing or bracing webs or gussets may be used as at 15, in Fig. 8, or 47 in Fig. 7. The exact construction of the central support or girder is immaterial, but it is important that the width of the box girder and counterweight support be confined to a narrow central strip of each leaf, desirably of the approximate proportion indicated. The maximum advantages of the invention cannot be achieved if this centrm girder is wider than one-fourth of the entire width of the traveled roadway or if multiple trunnions and racks and pinions are required for its support and operation.

As shown in Fig. 4, the girder Ill extends beneath the fixed roadway surface 16 rearwardly of the single supporting trunnion 17 and is provided near its rear extremity with a counterweight 18. The mass of concrete or the like used as a counterweight is augmented by the weight of the operating machinery hereinafter to As shown in Figs. 4, and 8, fioor joists l9 and 20 project laterally from the central supporting girder and upon these any desired roadway surface 21 is laid. The outer ends of the floor joists are connected to light girders or fascia 22 which may, as best shown in Fig. 3, have individual trunnions at 24 axially aligned with the main trunnions 17 and beyond which the supplemental girders 22 extend for engagement beneath the straps 25 in the lowered position of the lat. The purpose of this engagement is to relieve the load-carrying central girder of torsion when the trafiic is off center on the lowered leaf. Both because of the shortness of these rearward extensions of the auxiliary girders, and because of the lack of counterweight thereon, no pits may be required, the height of the trunnions above the pier being suflicient to accommodate their movement. However, by way of illustration, I have shown a construction in which the length of these rearward extensions of the auxiliary girders, is such that the piers have shallow recesses 27 to accommodate these girder ends as the leaf is raised.

The pier 30 may be T-shaped in plan, as shown in Fig. 3. Metal frames 31 mounted thereon support the main trunnion 17 and like frames 32 support the auxiliary trunnions 24. The main girder 10, like the auxiliary girders, desirably seats in the lowered leaf position against a transversely extending stop at 35, as shown in Fig. 4.

The pit 36 in the rearward extension 37 of the pier need only be sufficiently large to accommodate the main girder 10 and counterweight and the operating mechanism. For this reason, the rearward extension 37 of the pier is comparatively narrow. At the rear of the pit, and desirably extending somewhat above the level of the pier is a rack 40 of long radius for which the pier may be provided with a supporting structure 41 within the pit. A metal frame 42 (Fig. 4) supports the upper end of the rack.

The driving motor 43, gear train 44 and pinion 45 are all mounted on the rear end of the main girder 10, pinion 45 meshing with rack 40 so that the rotation of the pinion will cause it to traverse the rack to elevate the bridge leaf from the full line position of Fig. 4 to the dotted line position shown in that view. The fact that the driving action, as well as the counterweight forces are all transmitted through the single central girder, effects great savings in cost and eliminates sources of deterioration in operation as has already been explained.

As shown in Figs. 6 and 7, the location of the operating mechanism directly on the main girder 10 of the leaf is not an essential to the construction, although it is greatly preferred and has important advantages. If it be desired, a short rack of short radius may be provided at 400 on the under surface of the girder 160, concentric with the trunnion 17 and directly therebeneath, whereby the pinion 450, provided with a fixed mounting 46 on the pier, will transmit motion to the rack for the raising and lowering of the leaf.

be described.

which the traveled roadway is only wide enough to handle two lanes of traffic as compared with the four lanes of traflic for which the traveled roadway of the device of Figs. 1 to 5 is designed. In this construction, the fascia 220 merely connect the ends of the deep joists 190, instead of serving as auxiliary end supports, as in the device of Figs. 1 to 7. Where the single central box girder 101 is of this relative width and depth, no auxiliary girders and trunnions are required; the box girder being capable of resisting the torsional strains from the unbalanced loads of vehicles traversing its two lanes.

Whether the operating mechanism is carried by the leaf, as in Fig. 4, or is fixed as in Fig. 6, in either case there will be but one such mechanism for each leaf, instead of the two heretofore required and, in each case, the saving involves not only the elimination of the second mechanism but the saving of the chatter and distortion and irregularity of operation which follows from the use of dual mechanisms unless very expensive and delicate cross controls are employed.

The provision of sidewalks 48 and rails 59 is, of course, optional, and these features are illustrated only diagrammatically. If used, they can be fabricated in any desired 7 manner.

I claim:

1. A bascule bridge leaf having a longitudinal central girder extending for the full length thereof and upon which the leaf is substantially wholly dependent for support, said leaf being greatly in excess of the width of the girder and comprising laterally extending joists connected with said girder and means providing a roadway supported on said joists from said girder, and trunnion means upon which said girder is pivotally mounted, said girder extending rearwardly of the trunnion means and being provided with a counterweight substantially entirely supported therefrom, the width of the roadway being greatly in excess of the width of the counterweight, a single leaf operating mechanism having driving connections to said girder, and a pier supporting the said trunnion means and provided with auxiliary trunnion means laterally spaced at opposite sides of mentioned, said leaf having lightweight supplemental stringers adjacent the sides of its roadway and framing the joists and pivoted upon said auxiliary trunnion means, independently of said stringers, and said pier having a. pit portion narrower than the space between said auxiliary trunnions and adapted to receive said counterweight.

2. In a bascule bridge, the combination of pier means having laterally spaced portions between which there is an open pit, transversely disposed trunnion means car-- ried by the pier means, a stationary rack extending downwardly between the laterally spaced portions of the pier means, transverse stop means carried by the pier means rearwardly of the trunnion means, a main girder fulcrumed on the trunnion means and having a rearwardly projecting end approximately equal in radius to the rack and engaged beneath the stop means when the leaf is lowered, a pinion mounted on the rearwardly projecting ends of the girder and meshing with the rack, a motor in driving connection with the pinion mounted on the girder, a counterweight mounted on the rearwardly projecting end of the girder and movable therewith into the pit upon rotation of the pinion along the rack, means providing a traveled surface substantially wholly above said girder and projecting laterally at both sides of the girder and materially wider than the counterweight, and supporting framing for said traveled surface means connected with the girder and projecting laterally for substantial distances at both sides of the girder to constitute a bridge roadway forwhich said girder constitutes substantially the and aligned with the trunnion means first sole support when the leaf is lifted, said bridge leaf being movable about said trunnion means in response to the actuation of said pinion, and steadying means mounted on the pier means and offset laterally from the girder, said leaf having portions laterally offset from the girder and engaged with the steadying means to steady the leaf during use.

3. In a bascule bridge, the combination of a T-shaped pier having a head portion and a rearwardly extending stem provided with a pit, trunnion means carried by the head portion of the pier and disposed transversely across the median plane of the pit, a main girder fulcrumed on the trunnion means and having an end projecting rearwardly beyond said trunnion means and in swinging alignment with the pit, a counterweight carried by said end, power means for pivoting said girder on said trunnion means, laterally and outwardly extending transverse joists supported by said main girder, fascia girders connecting the ends of the joists, outer trunnions disposed on the ends of the pier head and to which said fascia girders are pivotally connected, a roadway surface on said joists, said main girder constituting substantially the sole support for said joists, fascia girders and roadway surface when said power means is actuated to pivot said main girder about its trunnion means and swing its rearwardly projecting ends and counterweight into said pit.

References Cited inethe file of this patent 

